let str = 'hello'  // string
let num = 123  // number
let flag = false // boolean
let und = undefined // undefined
let nu = null // null
let big = 123n  // big number
let s = Symbol('hello') 

let obj = {}
let arr = []  // new Array()   arr.__proto__.__proto__.__proto__ === Object.prototype
let fn = function() {}
let date = new Date()

// console.log(obj instanceof Object);
console.log(arr instanceof Object);
// console.log(fn instanceof Object);
// console.log(date instanceof Date);


// function test(obj) {
//   if (obj instanceof Object) {
//     return obj.name
//   }
// }
// test(['君君'])